“Iran’s role and its direct command of its Houthi proxy in this matter constitutes a clear act of aggression that targets neighboring countries, and threatens peace and security in the region and globally,” a statement released on Monday by the Saudi-led coalition said.

“Therefore, the coalition’s command considers this a blatant act of military aggression by the Iranian regime, and could rise to be considered as an act of war against the kingdom of Saudi Arabia,” the statement cautioned.

“The coalition command also affirms that the Kingdom reserves its right to respond to Iran in the appropriate time and manner,” the statement concluded.

Iran has backed the Houthi rebels, but denies arming them. There was no immediate response from Iran over the Saudi threat.

The Saudi statement says the closures will be temporary and “take into account” the work of humanitarian and aid organizations.

The war has claimed more than 10,000 lives and driven the Arab world’s poorest country to the brink of famine.

Yemen is one of several battlegrounds in the Middle East in which Iran is backing Shiite forces against Sunni forces, in many cases backed by Saudi Arabia, as part of the ongoing proxy war between Sunni and Shiite Muslims.